Production Of Neutron-rich Isotopes Research Articles

Statistical approach of nuclear multifragmentation with a realistic nuclear equation of state

In this work, Canonical Thermodynamical model for nuclear multifragmentation has been updated with realistic nuclear equation of state. Mass distribution, intermediate mass fragment multiplicity as well as isospin sensitive observables have been investigated with semi-microscopic approach of determining nuclear binding and excitation energies. Production of neutron rich isotopes as well as isoscaling and isobaric yield ratio parameters have been significantly modified due to inclusion of this realistic nuclear equation of state.

Exploring laser-driven neutron sources for neutron capture cascades and the production of neutron-rich isotopes

The production of neutron-rich isotopes and the occurrence of neutron capture cascades via laser-driven (pulsed) neutron sources are investigated theoretically. The considered scenario involves the interaction of a laser-driven neutron beam with a target made of a single type of seed nuclide. We present a comprehensive study over $95$ seed nuclides in the range $3\le Z \le 100$ from $^7_3$Li to $^{255}_{100}$Fm. For each element, the heaviest sufficiently-long-lived (half life $> 1$ h) isotope whose data is available in the recent ENDF-B-VIII.0 neutron sublibrary is considered. We identify interesting seed nuclides with good performance in the production of neutron-rich isotopes where neutron capture cascades may occur. The effects of the neutron number per pulse, the neutron-target interaction size and the number of neutron pulses are also analyzed. Our results show the possibility of observing up to $4$ successive neutron capture events leading to neutron-rich isotopes with $4$ more neutrons than the original seed nuclide. This hints at new experimental possibilities to produce neutron-rich isotopes and simulate neutron capture nucleosynthesis in the laboratory. With several selected interesting seed nuclides in the region of the branching point of the $s$-process ($^{126}_{51}$Sb, $^{176}_{71}$Lu and $^{187}_{75}$Re) or the waiting point of the $r$-process (Lu, Re, Os, Tm, Ir and Au), we expect that laser-driven experiments can shed light on our understanding of nucleosynthesis.

Further development of GALS setup at JINR

The aim of this paper is to report on the present status of the GAs cell based Laser ionization and separation Setup (GALS project) that is under construction at the Flerov Laboratory of Nuclear Reactions (FLNR) of JINR, Dubna. This project is directed on production of neutron-rich isotopes in the region of the magic N = 126 neutron number using multi-nucleon transfer reactions. The laser laboratory extension based on new TiSa lasers was performed, options of using a straight sextupole (SPIG) or an S-shaped quadrupole ion guides in the setup were compared based on the computer simulations, and the work on the rest of the GALS subsystems is being continued.

Nucleosynthetic yields from neutron stars accreting in binary common envelopes

Massive-star binaries can undergo a phase where one of the two stars expands during its advanced evolutionary stage as a giant and envelops its companion, ejecting the hydrogen envelope and tightening its orbit. Such a common envelope phase is required to tighten the binary orbit in the formation of many of the observed X-ray binaries and merging compact binary systems. In the formation scenario for neutron star binaries, the system might pass through a phase where a neutron star spirals into the envelope of its giant star companion. These phases lead to mass accretion onto the neutron star. Accretion onto these common-envelope-phase neutron stars can eject matter that has undergone burning near to the neutron star surface. This paper presents nucleosynthetic yields of this ejected matter, using population synthesis models to study the importance of these nucleosynthetic yields in a galactic chemical evolution context. Depending on the extreme conditions in temperature and density found in the accreted material, both proton-rich and neutron-rich nucleosynthesis can be obtained, with efficient production of neutron rich isotopes of low Z material at the most extreme conditions, and proton rich isotopes, again at low Z, in lower density models. Final yields are found to be extremely sensitive to the physical modeling of the accretion phase. We show that neutron stars accreting in binary common envelopes might be a new relevant site for galactic chemical evolution, and therefore more comprehensive studies are needed to better constrain nucleosynthesis in these objects.

New neutron-rich isotope production in 154 Sm+ 160 Gd

Deep inelastic scattering in $^{154}$Sm+$^{160}$Gd at energies above the Bass barrier is for the first time investigated with two different microscopic dynamics approaches: improved quantum molecular dynamics (ImQMD) model and time dependent Hartree-Fock (TDHF) theory. No fusion is observed from both models. The capture pocket disappears for this reaction due to strong Coulomb repulsion and the contact time of the di-nuclear system formed in head-on collisions is about 700 fm/c at an incident energy of 440 MeV. The isotope distribution of fragments in the deep inelastic scattering process is predicted with the simulations of the latest ImQMD-v2.2 model together with a statistical code (GEMINI) for describing the secondary decay of fragments. More than 40 extremely neutron-rich unmeasured nuclei with $58 \le Z\le 76$ are observed and the production cross sections are at the order of ${\rm \mu b}$ to mb. The multi-nucleon transfer reaction of Sm+Gd could be an alternative way to synthesize new neutron-rich lanthanides which are difficult to be produced with traditional fusion reactions or fission of actinides.

On-line production of neutron rich isotopes from uranium carbide targets

Experiments done using on-line mass separation of neutron-rich nuclei produced by 1 GeV proton beam on natural U by spallation reactions are performed to study the characteristics of different UCx targets. Special attention is devoted to reliably extract isotopic yields in case of complex decay schemes and to the valuation of release efficiency of some isotopic chains. New gamma-branching measuremet for 92Rb are obtained. In addition, a formalism is developed to disantangle the contribution of β-decay in the target from direct production by fission and to provide more consistent data for the interpretation of release curves. Some results are shown for the Cs and Rb isotopic chains.

Production of neutron-rich isotopes by fragmentation of 80 MeV/nucleon 59Co beam

using a primary beam of 59Co at 80 MeV/nucleon impinging on a berilium target, production cross-sections of neutron-rich fragments from projectile fragmentation have been measured at the Projectile Fragment Separator RIPS at the Institute of Physical and Chemical Research (RIKEN - Japan). The experimental production cross-sections ranging from Na to Ti for isotopes close to stability as well as for fragments at the neutron drip-line are compared to the results of the empirical parametrization EPAX.

Production of neutron-rich isotopes by one- and two-step processes in ISOL targets

The results are presented for an experiment that compares the difference between a one- and two-step reaction setup using 1 GeV protons. The rates of production from an on-line isotope separator target containing UC x are measured for isotopes in the neutron mass region of Rb and Cs. Some details about the measured results and predictions by the Monte Carlo models are discussed. The effects of the delayed release on the extracted efficiency are generalized using analytical models for application to a wide range of nuclear decay lifetimes.

Production of neutron rich isotopes in fission. A study for RNB facilities

The theoretical model for calculations of the fission product yields in the light-particle induced fission is discussed. A comparison of the production cross sections in fission of 238U by protons, thermal and fast neutrons, and photons is presented. The results of studies of the very asymmetric fission of 238U by protons and neutron at the moderate energy are reported.

Production of neutron-rich isotopes in fission of uranium induced by neutrons of 20 MeV average energy

In the context of a parameter study conducted by several laboratories for future European radioactive beam facilities based on fast-neutron induced fission, in particular for the SPIRAL-II project at GANIL, we have measured the yields of neutron-rich isotopes in the mass range of 88 to 144. These nuclei were obtained as fission products of natural uranium bombarded by neutrons of 20 MeV average energy emitted by a thick carbon target irradiated by 50 MeV deuterons. Yields have been measured using on-line mass separation with the ion-guide method. Compared with proton-induced fission at 25 MeV the magnitude of cross-sections, except for the symmetric region, is similar. Z-distributions of isobars have the same width, 0.7 charge units, but their maxima are shifted by about 0.8 charge units, favouring production of the neutron-richer isobars. Our data allow calculations of absolute cross-sections for fission of natural uranium induced by neutrons of about 20 MeV.

Exotic nuclei produced by fast neutrons in a liquid uranium target

The latest results of the research and development program Production d' Atomes Radioactifs Riches en Neutrons (PARRNe) at Institut de Physique Nucléaire (IPN) Orsay are presented. The production of neutron rich isotopes by fast neutron induced fission in a liquid depleted uranium target was measured. A comparison of the production rates with a uranium carbide (UCx) target is given.

A new pulsed release method for element selective production of neutron rich isotopes near 208Pb

A new method to reduce the isobaric contamination problem for the production of neutron rich Bi, Pb and Tl nuclei at on-line mass separators, based on the pulsed release of these radioactive species, is presented. The results of a feasibility study are reported.

Production of neutron-rich isotopes from the fragmentation of 28Si projectiles at plab=14.6 GeV/c per nucleon.

An investigation of the production of neutron-rich isotopes from the fragmentation of {sup 28}Si projectiles at {ital p}{sub lab}=14.6 GeV/{ital c} per nucleon was performed using the BNL-AGS-E814 spectrometer. We have measured the inclusive production cross sections of neutron-rich fragments ({sup 6}He, {sup 8}He, {sup 8}Li, {sup 9}Li, {sup 10}Be, {sup 11}Be, and {sup 13}B). We have also measured the transverse momentum distributions for {sup 6}He and {sup 9}Li, and the forward and transverse energy distributions associated with {sup 6}He production. The momentum distributions were analyzed in the context of the Goldhaber model. The question of whether the fragments are produced in the decay of the projectile following its electromagnetic excitation was also investigated.

Neutron-rich isotope production in reactions of 50Ti with natW and 238U and in fission of 238U with 13 MeV/u 20Ne

Isotopic yields of neutron-rich light fragments were measured at the Coulomb barrier in the reaction 50Ti+ 238U and compared with earlier results obtained from deeply inelastic nucleon transfer. No light fragments complementary in mass to the recently observed heavy fragments in cold massive transfer were detected. We also measured isotopic yields for nickel-to-europium products from the fission of 13 MeV/u 20Ne + 238U. The application of these reactions for production of neutron-rich isotopes is compared with other methods.

On the formation of carbon star characteristics and the production of neutron-rich isotopes in asymptotic giant branch stars of small core mass

On the formation of carbon star characteristics and the production of neutron-rich isotopes in asymptotic giant branch stars of small core mass